Definition
A controller-adaptable parameter, set per air traffic control sector, that defines how long a flight remains displayed in that sector's electronic flight data list after the aircraft has been handed off to the next sector or facility. When the interval expires, the flight automatically drops from the sector list.
Plain English
A timer that controls how long a handed-off flight stays visible on a controller's electronic strip list before it disappears. Each sector can set its own timer length.
Context Anchor
Seen in air traffic control automation and Pilot/Controller Glossary material; pilots normally encounter it when reading about how controller displays manage flight information.
Derivation
Built from plain English: 'Sector List' is the electronic list of flights a controller is working in their assigned airspace sector; 'Drop' refers to the flight being removed from that list; 'Interval' is the time period before that drop happens. Knowing each piece makes the function obvious — it's the wait-time before a handed-off flight falls off the list.
Why Pilots Care
Pilots do not calculate or use SLDI in normal cockpit operations, but understanding it helps separate ATC display timing from the actual clearance, radar contact, or control service being provided.
Intuition Check
Do not read “drop” as the aircraft being dropped from radar contact or ATC service. Here, it means the aircraft’s entry is removed from a controller’s electronic sector list after a set time.
Example Sentence 1
The facility adjusted the SLDI for the arrival sector so handed-off flights would remain on the list slightly longer during busy push periods.
Example Sentence 2
If an aircraft loses radar contact, the system will drop it from the list once the Sector List Drop Interval expires.